{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

lecture 2 - The Hardy-Weinberg Theorem A Null model The...

Info icon This preview shows pages 1–19. Sign up to view the full content.

View Full Document Right Arrow Icon
The Hardy-Weinberg Theorem A Null model The Hardy-Weinberg theorem Describes a population that is not evolving States that the frequencies of alleles and genotypes in a population’s gene pool remain constant from generation to generation provided that no other forces are at work.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
What would the genetic composition of a population be, if that population were NOT evolving?
Image of page 2
Definitions - review gene - the functional unit of heredity Allele – alternative forms of a gene locus – location on a chromosome (pl. loci)
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Definitions - review homozygote - same 2 alleles at a locus (AA, A 1 A 1 , etc.) Heterozygote - different alleles at a locus (Aa, A 1 A 2 , etc.) gametes (egg & sperm) are haploid zygote - fertilized egg, diploid
Image of page 4
If p and q represent the relative frequencies of the only two possible alleles (A & B) in a population at a particular locus, then ________________________ where p 2 and q 2 are the frequencies of the alternative homozygous genotypes and 2 pq represents the frequency of heterozygotes Hardy-Weinberg Equilibrium: Expected genotype frequencies
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
1. Chance of two independent events happening: Chance of getting heads flipping a coin= 50% Chance of getting heads flipping a coin a second time= 50% Chance two coin flips will both be heads = 25% 50% * 50% = 25% Combined chance of 2 independent events both occurring - multiplication problem
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
(general case) (specific case) If we know allele frequencies, can calculate genotype frequencies A 1 A 1 homozygote = p^2 A 2 A 2 homozygote = q 2
Image of page 8
(general case) (specific case)
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2. Chance of 1 or another event happening: Chance of getting 6 on one roll of die = 1/6 Chance of getting a 5 on one roll of a die = 1/6 Chance of getting a 6 or a 5 on one roll is 1/6 + 1/6 = 2/6 = 1/3 Chance of one OR another independent event - addition problem
Image of page 10
(general case) (specific case) If we know allele frequencies, can calculate genotype frequencies heterozygote = 2pq
Image of page 11

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
(general case) (specific case) A 1 A 1 + A 1 A 2 + A 2 A 2 p 2 + 2pq + q 2 = 1 (general case) 0.49 + 0.42 + 0.09 = 1 (specific case) If we know allele frequencies, can calculate genotype frequencies
Image of page 12
If we know genotype frequencies, can calculate allele frequencies
Image of page 13

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
A fruit fly population has a gene with 2 alleles, A1 and A2. Tests show that 80% of the gametes produced in the population contain the A1 allele. If the population is in Hardy Weinberg equilibrium, what proportion of the flies carry both A1 and A2? a. 0.04 b. 0.16 c. 0.20 d. 0.32 e. 0.84
Image of page 14
Population in H-W equilibrium is like deck cards Cards be shuffled - proportions of jacks, queens, etc. remain constant Alleles may be shuffled - proportions remain same
Image of page 15

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
…unless something changes them
Image of page 16
Hardy -Weinberg Equilibrium Principle Null model - model of no effect Based on assumptions: 1. No (natural) selection 2. Mating is random (panmictic) (likelyhood of mating with one mate over the other is equal) 3. Population is infinitely large 4. No gene flow from outside population 5. NO mutation (no new allele)
Image of page 17

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Hardy -Weinberg Equilibrium Principle Those assumptions rarely, if ever, met in nature So - why is a null model useful?
Image of page 18
Image of page 19
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern